Hantavirus explained: What to know after the cruise ship outbreak

Strips of paper with the word hantavirus printed on them, with one large strip in the center.

A cruise ship is currently stranded off the coast of West Africa after a suspected hantavirus outbreak killed three people and made several others very sick. Health officials have found a small number of confirmed and suspected cases of this rare virus on board.

What is hantavirus?

This class of virus was first identified in the Hantaan River area in Korea. Mice and other rodents often carry the hantavirus. Humans can contract the disease when they come into contact with infected rodents or their saliva, urine, and droppings.

Hantavirus was first recognized in the United States in 1993 (see "A mouse story") and has since been identified throughout the country. Although rare, the disease is potentially deadly, especially if it involves the kidneys, heart, or lungs.

What are the symptoms of hantavirus?

Early symptoms of the disease include fatigue, fever, and muscle aches, especially in the large muscle groups - thighs, hips, back, and sometimes shoulders. About half of all people infected also experience headaches, dizziness, chills, and abdominal problems such as nausea, vomiting, diarrhea, and abdominal pain. Four to 10 days later, other symptoms may appear, including coughing and shortness of breath, as the lungs fill with fluid.

The incubation period - the time between when a person is infected and when they begin to experience symptoms - is usually in the range of two to three weeks, but may be as long as eight weeks.

How do you get hantavirus?

Human-to-human spread of hantavirus is unusual, but may have occurred in the current outbreak on a cruise ship now off the coast of Cape Verde. So far in this outbreak, seven people have become ill with confirmed or suspected hantavirus; three of them have died. According to the World Health Organization, a rare type of hantavirus, called the Andes virus, may be responsible as it may rarely spread from person to person.

Hantavirus infections are not considered a significant risk to the public because of how rare they are and how rarely the virus spreads from person to person.

Hantavirus treatment

There is no specific treatment for hantavirus infection. An antiviral drug called ribavirin is sometimes recommended as it has proven effective for a specific type of hantavirus that causes kidney failure; however, it has not been proven effective for lung and heart involvement.

People who recognize signs of the infection early and promptly receive care may fare better than those who wait longer before seeking care. If the illness is recognized early, patients are given oxygen therapy to help them through the period of severe respiratory distress.

If you have been around rodents and have symptoms of fever, deep muscle aches, and severe shortness of breath, see your doctor immediately. Be sure to tell your doctor that you have been around rodents: this will alert your physician to look closely for any rodent-carried disease such as hantavirus. If hantavirus infection is suspected, take standard precautions, including distancing and wearing N95 masks, especially if the Andes virus is a concern.

Can hantavirus be prevented?

Many people who become ill with hantavirus say they did not see rodents or rodent droppings. This makes it all the more important to use good preventive methods - particularly in areas where the virus is known to exist - even if signs of rodents are not obvious.

Rodent control in and around the home remains the primary strategy for preventing hantavirus infection. This includes eliminating or minimizing contact with rodents in your home, workplace, or campsite. Discourage rodent habitation by sealing holes and gaps in your home or garage. Place traps in and around your home to reduce rodent infestation. And clean up any easy-to-get food.

A mouse story

In May 1993, an outbreak of an unexplained lung illness occurred in an area around the border of Arizona, New Mexico, Colorado, and Utah known as the Four Corners. A young, physically fit Navajo man suffering from shortness of breath was rushed to a hospital in New Mexico and soon died.

While reviewing the case, medical personnel discovered that the young man's fiance had died a few days before after showing similar symptoms, a piece of information that proved key to discovering the disease. An investigation combing the entire Four Corners region was launched by the New Mexico Office of Medical Investigations to find any other people with similar symptoms. Within a few hours, health officials had learned of five more young, healthy people who had all died after acute respiratory failure.

A series of laboratory tests failed to identify any of the deaths as caused by a known disease. At this point, the CDC Special Pathogens Branch was notified, and experts joined state health officials and the Indian Health Service, the Navajo Nation, and the University of New Mexico to confront the outbreak.

During the next few weeks, as additional cases of the disease were reported in the Four Corners area, physicians and other scientific experts worked to narrow down the list of possible causes. The particular mixture of symptoms and clinical findings pointed researchers away from some possible causes, such as exposure to an herbicide or a new type of influenza, and toward some type of virus. Samples of tissue from patients who had gotten the disease were sent to CDC for exhaustive analysis. Virologists at CDC used several tests, including new methods to pinpoint virus genes at the molecular level, and were able to link the pulmonary syndrome with a previously unknown type of hantavirus.

Researchers knew that all other known types of hantavirus were transmitted to people by rodents, such as mice and rats. Therefore, an important part of their mission was to trap as many different species of rodents living in the Four Corners region as possible to find the particular type of rodent that carried the virus. From June through mid-August of 1993, many types of rodents were trapped inside and outside homes where people who had hantavirus pulmonary syndrome had lived, as well as in pine groves and summer sheep camps where they had worked.

Among the rodents trapped, the deer mouse (Peromyscus maniculatus) was found to be the main host for the previously unknown type of hantavirus. Since the deer mouse often lives near people in rural and semi-rural areas - in barns and outbuildings, woodpiles, and inside people's homes - researchers implicated the deer mouse as the main transmitter of the virus. About 30% of the deer mice tested showed evidence of infection with hantavirus. Tests also showed that several other types of rodents were infected, although in lesser numbers.

Researchers concluded that years of drought followed by rainy weather had greatly increased the rodent population in the Four Corners area, putting rodents in much closer contact with humans and increasing the chances of transmission of hantavirus to humans during this period.